I’m not sure where to find Drupal logs with syslog on, and I couldn’t find any info as to whether platform recommends/cares Re: syslog vs dblog.
We do not currently support syslog. Unfortunately the binary which the Drupal syslog module relies on is not available, so enabling syslog in your Drupal instance will mean your logs have nowhere to go.
In general, application logs (outside of Drupal) are added to /var/log/app.log, and you can see most anything in /var/log/{$logname}.log with the cli command platform log {$logname}. You’ll find more information about the various log files in our developer documentation.
It’s not an official recommendation, but it’s possible that for Drupal 8,9
https://www.drupal.org/project/filelog
may work well enough for some types of logging needs.